Remote control system for a vehicle

ABSTRACT

A remote control system for precisely identifying a distance from the vehicle to an entry key and favorably controlling a vehicle-mounted device such as a door corresponding to the distance. The system comprises a transmitter transmitting different types of response demand signals within a predetermined communication area outside the vehicle, a vehicle mounted receiver for receiving a response signal released from a portable transmitter/receiver in response to the reception of the response demand signal, a controller controlling the vehicle mounted device corresponding to the reception of the response signal by the vehicle mounted receiver. Locking and/or unlocking door(s) of the vehicle are controlled on the basis of whether or not the receiver receives the response signal to a response demand signal other than one having the largest communication area.

This application is a continuation of prior application Ser. No.09/612,315 filed Jul. 7, 2000, now U.S. Pat. No. 6,778,065.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a remote control system for a vehiclewhich can automatically lock and unlock the door(s) of a vehicle inwireless communication and more particularly to a remote control systemfor a vehicle which can automatically lock the door(s) of a vehicle whena user (driver) who carries with him an electronic or entry key (with aportable transmitter/receiver) which includes an identification codeassigned to the vehicle walks away a predetermined distance from thevehicle and automatically unlock the same when the user comes back tothe distance.

2. Description of the Related Art

Lock/unlock remote-control systems for vehicle doors are known having aso-called, “welcome function”. In the systems, every user (driver) of avehicle owns an entry key (with a portable transmitter/receiver) whichupon receiving a response demand signal that is transmitted from atransmitter installed in the vehicle and is receivable within apredetermined range about the vehicle (which may be referred to as“having a predetermined communication area” hereinafter), can transmit aresponse signal carrying a unique identification code assigned inadvance to each vehicle. When the user walks away from the predeterminedrange of the vehicle and its entry key is disabled to receive theresponse demand signal and thus to transmit back the response signal,the door of the vehicle is automatically locked. When the entry keymoves into the predetermined range and its response demand signal isreceived by the transmitter/receiver which then responses thereto tosend back a response signal, the door is automatically unlocked.

For example, some of such conventional “welcome function” basedlock/unlock remote-control systems for vehicle doors are disclosed inJapanese Patent Laid-open Publications (Heisei)5-106376 and(Heisei)10-25939 in which a transmitter mounted on a vehicle is providedfor intermittently transmitting a response demand signal having apredetermined communication area and, when receiving a signal respondingto the response demand signal from an entry key which is carried by theuser of a vehicle and moves into the predetermined communication area,examining whether the response signal is valid (regular) or not (welcomecode examination). When the response signal has been examined to bevalid, the door(s) of the vehicle is automatically unlocked. On thecontrary, when the response signal is not valid or when the entry keystays out of the predetermined communication area and thevehicle-mounted transmitter receives no response signal, the doorremains locked.

Accordingly, when the user of the vehicle carrying the entry key simplywalks away from the predetermined range of the vehicle, the door of thevehicle can automatically be locked without paying any attention to oroperating the entry key. When the user comes into the range, the doorcan automatically be unlocked. This requires no boresome actions ofunlocking the door for riding the vehicle as well as contributes to theprevention of failing to lock door(s), and of vehicle theft.

The conventional systems have some advantages, particularly once thecommunication area is preset to a smaller size (for example, one meterin radius), the systematic locking of the door can easily be confirmedafter getting off the vehicle, the power consumption for transmittingsignals can be as small as not hostile to a battery, and the ID code(uniquely assigned to a vehicle) can hardly be intercepted by any otherparties. The locking of the door may be easily confirmed by auditorilyand visually perceiving the sound of a door locking mechanism and theshift of an inside door lock knob to the lock position.

Another conventional system disclosed in Japanese Patent Laid-openPublication (Heisei)10-153025 is provided in which a transmissionantenna for detecting the approaching of an object into a middle-sizedarea around a vehicle is mounted on the vehicle in addition to anantenna for transmitting the response demand signal. Upon detecting theapproaching of the object or a driver into the middle-sized area, thevehicle releases the response demand signal with a small-sizedpredetermined communication area and, when receiving a response signalto the response demand signal from the entry key of the right driver,unlock the door. Also, a second transmitting means having a greatercommunication area is provided for locking the door. The door is thuslocked when the communication to the entry key with the secondtransmitting means is disabled.

According to the conventional systems, when the communication area forthe response demand signal is set to be wide enough to detect the driverapproaching into the area of the vehicle at an earlier occasion, thedoor(s) can be unlocked positively before the driver reaches thevehicle. This eliminates the need of the door being unlocked by thedriver or user and provides the ease of getting in the vehicle withoperating only a door outer handle, hence improving the utility.

However, as the communication area is wide, the locking of the door willbe carried out only when the user departs further from the vehicle,hence causing the user to confirm the door locking (through listening tothe sound of the door locking mechanism or viewing the shift of theinside door lock knob to the lock position) with much difficulty. Also,while the user with the entry key walks about or pursues a job (e.g.ordering throughout the trunk room), the door locking is not performedand it may fail to protect articles in the vehicle from a thief.

In particular, when the user with the entry key is departing from thevehicle, its back is often turned to the vehicle. The wider thepredetermined communication area, the longer the period of the doorremaining unlocked is extended and thus the higher the risk of beingthieved will be increased. Also, the wider communication area requires ahigher level of power for transmitting the response demand signal andthe power consumption will be soared up drawing more power from thebattery.

For compensation, a modification is proposed such as disclosed inJapanese Patent Laid-open Publication (Heisei) 10-25939, where thecommunication area is reduced (about one meter in radius) allowing theresponse demand signal to be not received in a shorter distance from thedoor thus to lock the door. This permits the door locking to be easilyconfirmed, the ID code (ID number) to be hardly intercepted, and thepower for signal transmission to be minimized, hence lowering the powerconsumption.

However, the above modification will hardly ensure the unlocking of thedoor. It is common in the art for minimizing the power consumption fortransmitting the response demand signal that the response demand signalfrom the vehicle is usually transmitted intermittently. With the widercommunication area, the user moving in the wider area is able tocommunicate with the vehicle, even if the response demand signal istransmitted with longer intermission period. Accordingly, the door issurely unlocked before the user arrives at the vehicle.

With the smaller communication area, however, when the user rushes tothe vehicle in less time through the communication area, thecommunication between the vehicle-mounted transmitter and the entry keymay not be completed until the user arrives at the vehicle. This causesthe door to remain locked and its door outer handle may have to beoperated a number of times without success. As a result, the entry keysystem will be lost in commercial value. As a further modification, theperiod of the intermittent transmission of the response demand signalmay be shortened. This will however increase the power consumption andcause more power be drawn from the battery.

On the other hand, the conventional system disclosed in theabove-mentioned Japanese Patent Laid-open Publication (Heisei)10-153025allows the power for transmitting the response demand signal to bepossibly decreased, but it requires the extra transmission antenna fordetecting the invading of an object, hence increasing the complexity ofthe overall arrangement and thus the cost of the system. Also, the powerconsumption will be increased by the additional equipment. Moreover, theabove system transmits the response demand signal even when any otherpersonal or creature than the right entry key (user) advances close tothe vehicle, hence requiring more improvement for the power consumption.Since the communication area is too small to examine whether the entrykey is right or not as required before accepting the unlocking, the doormay remain not unlocked when the user or driver rushes to and arrives atthe vehicle. This will result in the misconduct of the automaticunlocking function.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a remote control systemfor a vehicle which can predictably control a vehicle mounted devicesuch as a door of the vehicle corresponding to the distance from thevehicle to an entry key.

As a first feature of the present invention, the remote control systemfor a vehicle comprises: a transmitter mounted on the vehicle fortransmitting a plurality of response demand signals which are receivablewithin different sizes of a predetermined range outside the vehicle; aportable transmitter/receiver for receiving the response demand signalsand sending back a response signal; a receiver mounted on the vehiclefor receiving the response signal sent back from the portabletransmitter/receiver; and a controlling means for controllingvehicle-mounted components corresponding to the reception of theresponse signal by the receiver, wherein said controlling means arrangedto control at least either unlocking or locking of the door(s) of thevehicle depending on whether the response signal to a type of theresponse demand signal other than a particular response demand signalbeing receivable in the largest size of the predetermined range isreceived or not by the receiver.

As a second feature of the present invention, the transmitterintermittently transmits different types of the response demand signalsreceivable within corresponding sizes of the predetermined range, andthe controlling means identifies a particular predetermined range wherethe portable transmitter/receiver is located on the basis of theinterval between receptions of the response signals and controls thevehicle-mounted components in a predetermined mode, corresponding to thesize of the predetermined range where the transmitter/receiver islocated.

As a third feature of the present invention, various types of responsedemand signals are intermittently transmitted at different intervalssuch that the transmission of one type of the response demand signalreceivable within a smaller predetermined range is transmitted at leastonce between two adjacent transmitted timings of another type of theresponse demand signal receivable in a wider predetermined range.

As a fourth feature of the present invention, the response signals sentback from the portable transmitter/receiver are discriminatable oneanother according to which size of the predetermined range of therespond demand signal that the respond signals respond to.

As a fifth feature of the present invention, when the disembarkation ofthe user is detected and the user is departing from the vehicle, a typeof the response demand signal receivable within the smallest size of thepredetermined range is transmitted from the transmitter, and when theresponse signal showing reception of the response demand signalreceivable in the smallest size of the predetermined range is no morereceived by the receiver mounted on the vehicle, another type of theresponse demand signal receivable within the second smallest size of thepredetermined range is begun to be transmitted from the transmitter and,in a similar manner, when the response signal to a type of the responsedemand signal receivable in a relatively smaller size of thepredetermined range is no more received by the receiver mounted on thevehicle, a further type of the response demand signal receivable withina relatively larger size of the predetermined range is begun to betransmitted in sequence from the transmitter.

As a sixth feature of the present invention, when the entry key isapproaching to the vehicle and the response signal to the type of theresponse demand signal receivable within the largest size of thepredetermined range is first received by the receiver mounted on thevehicle, the response demand signal receivable within second largestsize of the predetermined range is transmitted from the transmitter andthen a response demand signal receivable within a relatively smallersize of the predetermined range is transmitted in sequence from thetransmitter.

As a seventh feature of the present invention, when the embarkation ofthe user is detected by the embarkation detecting means, a type of theresponse demand signal receivable within the vehicle is transmitted fromthe transmitter.

According to the first feature of the present invention, the distancefrom the vehicle to the user carrying the portable transmitter/receiver(entry key) can precisely be identified thus to control the vehiclemounted device such as the door(s) at an optimum length of the distance,hence improving the utility of controlling the vehicle mounted devicesuch as unlocking and locking the door is compatible with the anti-thieffunction.

According to the second feature of the present invention, the distancerange from the vehicle to the user carrying the portabletransmitter/receiver can be identified on the basis of the intervalbetween receiving timings of the sent-back response signal on thevehicle even if characteristic codes included in the response signalsare not different each other, which response signals are sent back fromthe portable transmitter/receiver that responds to a plurality types ofthe response demand signal receivable within their respective sizes ofthe predetermined ranges which are different each other. Hence, thevehicle mounted device can favorably be controlled depending on thedistance as well as the construction of the transmitter of the portabletransmitter/receiver and the code identifying action of the controllingmeans on the vehicle can significantly be simplified.

According to the third feature of the present invention, the responsesignal is also intermittently released from the portabletransmitter/receiver, thus providing the same effects and advantages asdescribed just above.

According to the fourth feature of the present invention, as theresponse signals released from the portable transmitter/receiver inresponse to reception of the response demand signal are different eachother based on the different sizes of the receivable ranges of thedemand signals, the distance from the vehicle to the portabletransmitter/receiver can be identified only from the response signalreceived and the optimum control of the device mounted on the vehiclecan be performed in accordance with the distance.

According to the fifth and sixth features of the present invention, atthe disembarkation of the user, as the portable transmitter/receivercarried by the user departs far from the vehicle, the transmission ofthe response demand signal receivable in a wider size of thepredetermined range is executed in sequence and the transmission of theresponse demand signal receivable in a smaller size of the predeterminerange is canceled. As the potable transmitter/receiver comes from fartowards the vehicle, on the other hand, the transmission of the responsedemand signal with a relatively smaller predetermined receivable rangeis not executed before the response signal responding to the responsedemand signal with a relatively larger predetermined receivable range isreceived by the vehicle.

More particularly, while the portable transmitter/receiver is out of thelargest predetermined receivable range, the response demand signalreceivable in the largest predetermined range only is transmitted. Onlywhen the response signal responding to the response demand signalreceivable in the largest predetermined range is received by thevehicle, the transmission of the response demand signal being receivablein a smaller size of the predetermine range and used for actuallycontrolling the unlocking and locking of the door is executed.Therefore, the transmission of the response demand signal is minimizedhence reducing the consumption of a power from a battery equipped on thevehicle.

According to the seventh feature of the present invention, the usercarrying the portable transmitter/receiver in the vehicle can readily beacknowledged, and the vehicle mounted device in the vehicle iscontrolled on the basis of the response signal from the portabletransmitter/receiver responding to a particular type of the responsedemand signal receivable within the vehicle, hence improving theanti-thief function.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a structure of the first embodiment ofthe present invention;

FIG. 2 is a timing chart illustrating the automatic unlocking action ofa door in the first embodiment of the present invention when the drivercarrying the entry key moves to the vehicle and embarks;

FIG. 3 is a timing chart illustrating the automatic locking action ofthe door in the first embodiment of the present invention when thedriver disembarks and the entry key departs from the vehicle;

FIG. 4 is a part of the main flowchart showing an action of the firstembodiment of the present invention;

FIG. 5 is the remaining part of the main flowchart showing an action ofthe first embodiment of the present invention;

FIG. 6 is a flowchart showing the transmission of a response demandsignal with timer interruption in the first embodiment of the presentinvention;

FIG. 7 is a flowchart showing a refresh 1 process in FIG. 4;

FIG. 8 is a flowchart showing a refresh 2 process in FIG. 4;

FIG. 9 is a flowchart showing a part of a welcome process in FIG. 4;

FIG. 10 is a flowchart showing the remaining part of the welcome processin FIG. 4;

FIG. 11 is a flowchart showing an immobilizing checking process in FIG.4;

FIG. 12 is a flowchart showing the transmission of an I response demandsignal with timer interruption in the first embodiment of the presentinvention;

FIG. 13 is a schematic view showing the relation between the controloperations and the distance from the vehicle to the entry key in thefirst embodiment of the present invention;

FIG. 14 is a schematic view showing the relation between the controloperations and the distance from the vehicle to the entry key in anotherembodiment of the present invention;

FIG. 15 is a diagram showing an exemplary format of the response demandsignals preferably applicable to the present invention;

FIG. 16 is a diagram showing an exemplary format of the response signalfor immobilizing operation preferably applicable to the presentinvention;

FIGS. 17 and 18 are main flowcharts showing the action of a furtherembodiment of the present invention as combined;

FIG. 19 is a flowchart showing a part of a welcome process in FIG. 17;

FIG. 20 is a flowchart showing the transmission of the response demandsignal with timer interruption in a further embodiment of the presentinvention;

FIGS. 21A and 21B are a timing chart showing the transmission of theresponse demand signal in a still further embodiment of the presentinvention as combined;

FIG. 22 is a timing chart illustrating the automatic locking action ofthe door in the still further embodiment of the present invention whenthe driver disembarks and the entry key departs from the vehicle;

FIG. 23 is a timing-chart illustrating the automatic unlocking action ofa door in the still further embodiment of the present invention when thederiver carrying the entry key moves to the vehicle and embarks;

FIGS. 24 and 25 are main flowcharts showing in a combination the actionof the still further embodiment shown in FIGS. 22 and 23; and

FIG. 26 is a flowchart showing a part of a welcome process in FIG. 24.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An entry key system for a vehicle according to first embodiment of thepresent invention will be describe in more detail referring to theaccompanying drawings. Before starting the main description, somedefinitions on the flags at 1 of the bit and the timers employed in thedescription and the drawings are explained as listed below.

-   -   AREC=reception of A code;    -   ATM=transmission of A response demand signal;    -   BCHG=start of examining the shift from small B response demand        signal to large B response demand signal;    -   BLTM=transmission of large B response demand signal;    -   BREC=reception of B code;    -   BSTM=transmission of small B response demand signal;    -   I(variable)=the number of consecutive receptions of A code;    -   IMCHK=start of immobilizing checkup;    -   IMDONE=finish of immobilizing checkup;    -   IMOK=result of immobilizing checkup;    -   m(variable)=setting in timer T-OUT;    -   MOD(n,m)=remainder of n/m;    -   n(variable)=setting for the kind of response demand signals to        be transmitted;    -   OUT=the entry key is out of communication area for A response        demand signal;    -   RCHK=timer T-OUT has started for examining the entry key is not        near about vehicle;    -   RF1/2=finish of refresh procedure 1, 2, respectively;    -   T-BCHG=timer for setting exchange of B response demand signals;    -   T-IMCHK=timer setting time for immobilizing checkup;    -   T-OUT=timer setting time for judging that the entry key is out        of communication area for A response demand signal;    -   T-WR1/2=first and second timers each for measuring intervals of        signal reception;    -   timer interrupt permission bit for response demand signal=timer        interruption permission for transmission of response demand        signal.

A first embodiment of the present invention will be described in theform of a remote control system for a vehicle referring to the blockdiagram of FIG. 1.

A smart entry unit 1 comprises a power supply circuit 2 such as abattery equipped on the vehicle, an input/output circuit 3 connected toLF (low frequency) transmitter circuits 9 a to 9 c, a bus communicationcircuit 4 connected by a communication line 32 to an ignition SW unit 10which will be described later, a memory circuit 5, an MOSFET circuit 6,an input circuit 7, and a CPU 8 connected to above-mentioned circuitcomponents for controlling their actions. The CPU 8 is further connectedto an RF receiver circuit 9 f. The input circuit 7 is connected to amanual SW 7 a for setting the system to a manual mode in which it isresponsive to only a manual code derived by manual operation from anentry key 50 which is described later, as well as a parking SW 7 b, fourdoor SWs 7 c, an engine hood SW 7 d, a door key cylinder SW 7 e, and soon.

The entry key 50 which is usually carried and manipulated by a driver oruser of the vehicle comprises an RF circuit 51 for transmitting an RFsignal from an antenna, an alarm/display 52 such as a buzzer, arectifier trigger (TRIG) circuit 53 for processing LF signals receivedwhich are transmitted from the LF transmitter circuits 9 a to 9 c, a CPU54, a battery 55, manual switches 56 and 57 for transmitting manualcodes for manually locking and unlocking the door, and a switch 58 forallowing/prohibiting the manual operation. The switches 56 and 57 may bemodified in to a single switch for repeating alternately the lock andunlock actions.

The ignition SW unit 10 comprises a bus communication circuit 11 forexchanging signals via the communication line 32 with the smart entryunit 1, a power supply circuit 12, a memory circuit 13, an immobilizing(anti-thief functioning) antenna 14, a low frequency (LF)transmitter/receiver circuit 15, a key SW 16 for detecting theinsertion/extraction of a key, an ignition (IGN) SW 17, an IGN positiondetector 18 for detecting the contact position of the IGN SW 17, a motor19 for actuating a rotary contact of the IGN SW 17, a motor driver 20for driving the motor 19, an auxiliary (or emergency) key 21 which isinserted and extracted to and from the key cylinder, an interlock ACT(actuator) 22 for prohibiting the removal (or extraction) of theauxiliary key 21, an ACT driver 23 for driving the interlock ACT 22, anda CPU 24 for controlling the actions of the above-mentioned components.The CPU 24 is also connected to a quick start SW 31 for starting theengine.

The operation of the smart entry unit 1 and the entry key 50 willschematically be described referring to the timing charts of FIGS. 2 and3 and the schematic view of FIG. 13. FIGS. 2 and 3 illustrate thewelcome function in which the door of the vehicle is unlocked and lockedin response to the detection of the user carrying the entry key 50 (whomay hence be simply referred to “entry key” hereinafter) coming close tothe vehicle 1 for boarding and leaving from the vehicle 1 after gettingoff, respectively. In these figures, the height of the bars of theresponse demand signals represents the intensity of the signals thusindicating the size of the communication area (receivable range).

When the entry key is outside of and distanced significantly from thevehicle of which the door remains locked in a disembark or parking mode,an A response demand signal (of e.g. 100 kHz) shown at the left side endin FIG. 2 is transmitted from the vehicle at equal intervals of a firstpredetermined time (y seconds) and with an intensity corresponding tothe maximum communication area (for example, 4 to 5 meters in radius)denoted by A in FIG. 13. As the driver carrying the entry key moves intothe communication area A for the A response demand signal, the entry keyreceives the A response demand signal at the moment t1 and transmits asend-back signal or a response signal responding to the A responsedemand signal which includes an A code and may be referred to as “Acode” hereinafter. The format of the response signal will be explainedlater in more detail referring to FIG. 15.

The vehicle, when receiving the response signal and judging that theresponse signal received is valid, releases a large-area B responsedemand signal (e.g. of 300 kHz and having a one-meter-radiuscommunication area denoted by B (large) in FIG. 13) from t2 at equalintervals of a second predetermined time (x seconds). It is assumed y>xor more specifically, y=3x in this embodiment. Upon receiving the Blarge response demand signal at t3, the entry key 50 releases a responsesignal which includes a B code and may be referred to as a “B code”hereinafter. When it is judged that the response signal including the Bcode is valid, the door of the vehicle is unlocked.

As the door is opened at t4 (door SW is on) and then closed at t5, it isdetermined that the driver has embarked and an I (immobilizing) responsedemand signal designated its communication area as in the interior ofthe vehicle is transmitted. When the entry key then releases a responsesignal to the I response demand signal which include an I code(immobilizing code), the vehicle carries out immobilizing checkup(immobilizing code examination) for deciding whether the I code receivedis valid or not. When the I code is valid, the transmission of the Iresponse demand signal is canceled and an FI-ECU 33 is switched at t6into the engine enabling mode.

Then, upon the ignition SW (IGN SW) being turned to the ON position att7, the transmission of both the A and B response demand signals isstopped and simultaneously a refresh 2 process is commenced as will bedescribed later. The transmission of the A and B response demand signalsmay be stopped, instead, upon judging that the I code is valid or inresponse to the on/off action of the door switch triggered by theopening and closing of the door.

The movement of the vehicle 1 is stopped and then as the IGN SW isturned from the ON position to the ACC position at t1 as shown in theleft end of FIG. 3, the FI-ECU 33 is switched to the engine disablingmode. When the door SW is shifted from the OFF position (door closed) tothe ON position (door opening) at t2 in the door unlock mode, it isjudged that the driver is about to disembark and the transmission of a Bsmall response demand signal (e.g. of 300 kHz having substantially a0.5-meter-radius communication area denoted by B (small) in FIG. 13) isthen commenced. This is followed by transmitting the B small responsedemand signal at equal intervals of the second predetermined time (xseconds) from the vehicle. Then, as the door SW is shifted from the ONposition to the OFF position (door closed) at t3, the I response demandsignal is transmitted at the predetermined intervals.

When the entry key is disembarked, it enables to receive not the Iresponse demand signal but the B small response demand signal. Then aresponse signal to the B small response demand signal including the Bcode is released. When the response signal including the B code isreceive and is judged to be valid at t4, the A response demand signal iscommenced to be transmitted while the transmission of the I responsedemand signal is stopped. The entry key continues to release the A and Bcodes while receiving both the A and B small response demand signals.

As the driver with the entry key moves away from the vehicle and stepsout from the B small area shown in FIG. 13, it is disabled to receivethe B small response demand signal and no response signal with B code tothe B response demand signal shall be sent back. When the B code is notreceived by the vehicle after a predetermined period from the receptionof the A code (at t5 in FIG. 3), the B response demand signal isswitched from the B small signal to the B large signal. As the B code isno more received after the predetermined period while the A code isreceived and its welcome code examination is executed (i.e. in thisembodiment, only the A code is continuously received but the B code hasnot been received in y seconds), the door is then locked at t7 when thefinal A code is examined to be valid.

After t8 when the setting (m seconds) of the T-OUT timer has elapsedsince the entry key is far enough away from the vehicle not to receivethe A response demand signal and thus not to send back the A code, theintermittent transmission of only the A response demand signal at theintervals of y seconds is maintained. Alternatively, as denoted by thedotted line in FIG. 3, the door may be locked at t5 when the A code isreceived just after the reception of the B code at the estimated momentis not executed.

The operation of the smart entry unit 1 will now be describedschematically referring to the flowcharts of FIGS. 4 and 5.

Upon energized, the system is initialized in its entirety (Step S1). AtStep S2, it is examined whether the ignition switch (referred to an IGNSW hereinafter) is turned on or not. When the IGN SW is turned off bythe driver to stop the vehicle at t1 in FIG. 3, the procedure goes toStep S3 where the refresh 1 process, i.e. the initialization of flagsfor the (anti-thief) immobilizing system, is carried out. This processat Step S3 will be explained later in more detail referring to FIG. 7.

This is followed by Step S5 where it is examined whether the door isunlocked or not. At Step S6, it is examined whether or not the door SWis turned from the ON position to the OFF position (i.e. whether theopened door of the vehicle is closed or not). As it is judged “NO” atStep S6 while the door is opened for disembarkation, the procedure jumpsto Step S9 where it is examined whether or not the manual SW7 a isturned on for shifting the system to the manual mode where the door canbe unlocked and locked using the manual switch. In normal, the manual SW7 a remains turned off (i.e. the manual mode is not selected) and it isjudged “NO”. It is then examined at Step S10 whether or not the door SWis turned from the OFF position to the ON position (i.e. the closed dooris opened).

As the door is opened for disembarkation, the door switch is turned fromthe OFF position to the ON position and it is judged “YES” at Step S10.Then, Step S11 follows where it is examined whether the BREC flag is 1or not (i.e. the B code is received or not). In the beginning, the Bcode is not received and the procedure advances to Step S12 where theBSTM flag is set to 1 and the variable n for determining the type of theresponse demand signal (A, B small, or B large) is reset to 0.

Step S12 is a process of selecting the type of the response demandsignal to be transmitted and, as will be explained later, the B smalltype having a smaller communication area is set. At Step S13, the timerinterruption permitting bit for enabling the transmission of theresponse demand signal is set, i.e. the transmission of the responsedemand signal by timer interruption is enabled.

Then Step S14 follows where it is examined whether the valid ID code isreceived or not. When it is affirmative, it is then judged at Step S15what the function code is. More specifically, it is examined whetherreceived signal is the response signal (A code or B code) from the entrykey 50 or the manual code for the manual operation. In the beginning, itis judged “NO” at Step S14 and the procedure moves to Step S15A where itis examined based on the IMCHK flag whether the immobilizing checkup isfinished or not. At the time, the immobilizing checkup is not performedand the procedure jumps to Step S30 (in FIG. 5). Similarly, it is judged“NO” at Step S30 and the procedure goes to Block S41. At Block S41, theflags for the welcome function are initialized when the code is notreceived during a predetermined period of time.

In fact, it is examined referring to the OUT flag at Step S31 whether ornot the entry key is out of the communication area for the A responsedemand signal. In the beginning, it is not registered (i.e. OUT flag=0)that the entry key is out of the communication area for the A responsedemand signal. It is then examined at Step S32 whether the RCHK flag is1 or not (i.e. the T-OUT timer for setting time duration to determinethat the entry key is not adjacent to the vehicle, has been started ornot) When it is judged “NO”, the procedure goes to Step S33 where theT-OUT timer is set to m seconds. It is preferable that m satisfies msec>y(=3x) sec≧z sec where y is the interval of transmission (or cycle)of the A response demand signal, x is the interval of transmission ofthe B response demand signal, and z is the interval of transmission ofthe I (immobilizing) response demand signal, as shown in FIG. 2. Then,at Step S34, the RCHK flag is set to 1 for starting the T-OUT timer.

This is followed by Step S35 where it is examined whether the T-OUTtimer is turned to zero as the setting time of m seconds has beenelapsed. In the beginning, the setting time of m seconds is not elapsedand thus the procedure returns back to Step S2.

As the driver disembarks and the door is closed, the door switch isshifted from the ON position to the OFF position allowing Step S6 tojudge “YES”. The procedure thus goes to Step S7 where the refresh 1 flagis reset to 0. Step S8 follows where the timer interruption permittingbit for permitting the transmission of the I response demand signal isinitiated to enable the transmission of the I response demand signalwith timer interruption. Then, the procedure moves to Steps S14, S15A,and S30, and Block S41 and returns back to Step S2.

As the entry key 50 is moved out of the vehicle, it receives the B smallresponse demand signal and sends back the B code. The B code from theentry key 50 is received by the receiver on the vehicle and qualified asa valid code and it is then judged “YES” at Step S14. The procedure thusgoes to Step S15 where it is examined whether or not the signal codereceived is the manual code sent from the entry key 50 by the manualswitch operation for locking and unlocking the door. When it is judged“YES”, the procedure advances to Step S16 where the manual operation isenabled (which is a process to interpret the code issued through themanual switch operation and will be explained in no more detail).

As the received code is the B code carried on a response signal to theresponse demand signal at present, it is judged “NO” at Step S15 and theprocedure moves to Step S17 where it is examined whether the manual SWis turned on or not. When it is judged “YES” at Step S17, the procedurereturns back to Step S2. As “NO” is given at Step S17, however, theprocedure goes to Step S18 where the welcome function process forunlocking and locking the door in response to the result of the welcomecode judgment is executed.

Welcome Function Process at Disembarkation

The welcome process at Step S18 in FIG. 4 will now be explained in moredetail referring to FIGS. 9 and 10. It is assumed that the driver stopsthe engine, disembarks, and departs with the entry key from the vehicle.As described previously, the disembarkation of the driver is followed byStep S12 (FIG. 4) for selecting the transmission of the B small responsedemand signal and resetting the variable n to 0 and Step S13 forenabling the transmission of the B response demand signal with timerinterruption. Then, the welcome process is commenced at Step S18 inresponse to the reception of the correct B code.

The welcome process starts with Step S171 where it is examined whetherthe signal code received from the entry key is the A code or not. In thebeginning, since the A response demand signal is not transmitted it isjudged “NO”, allowing the procedure to goes to Step S201. When it isjudged at Step S201 that the received code coincides with the right Bcode, the procedure moves to Step S202 where the BREC flag representingthe reception of the B code is set to 1 while the number of consecutivereceptions of the A code denoted by I is set to zero. Step S204 followswhere the door is unlocked.

It is then examined at Step S209 whether the AREC flag is 1 or not. Asthe A code is not received by now, it is judged “NO”. The procedurehence goes to Step S210 where the ATM flag is set to 1 for enabling theintermittent transmission of the A response demand signal. At Step S211,the variable n is set to 0. At Step S212, the timer interruptionpermitting bit for the I response demand signal is cleared off toinhibit the transmission of the I response demand signal. At Step S214,the BCHG flag is set to 0. While the B code only is receivedcontinuously, the above steps are repeated.

When the A code is released from the entry key in response to thereception of the A response demand signal and received by the vehicle,it is judged “YES” at Step S171. The procedure then goes to Step S172where the AREC flag is set to 1 while the OUT flag and the RCHK flag areturned to 0 to register that the entry key 50 is within thecommunication area for the A response demand signal and reset the T-OUTtimer. At next Step S173, the variable I indicating the number ofconsecutive reception of the A code is increased by 1 for updating (I isthus turned to 1). It is then examined at Step S174 whether or not thevariable I is turned to 2 (for example). In the beginning, I is not 2and the procedure jumps to Step S180.

It is examined at Step S180 whether the BSTM flag indicating theselection of the B small response demand signal is 1 or not. As the BSTMflag is 1 so far, it is judged “YES” and the procedure moves to StepS181 where it is examined whether the BCHG flag for causing the Bresponse demand signal being switched from the B small to the B large is1 or not. As the BCHG flag is now 0, the procedure goes to Step S182 forsetting the BCHG timer to, for example, 30 seconds.

The setting time for the BCHG timer may be determined on the basis ofexperiments or actual measurements to a duration enough to allow theentry key to get away enough from the vehicle and step out of thecommunication area for the B large response demand signal. Then, theprocedure moves to Step S184 where the BCHG flag is shifted to 1. It isthen examined at Step S185 whether the BCHG timer is turned to zero ornot. In the beginning, the timer is not zero and the procedure returnsback to Step S2.

As the entry key steps out of the communication area for the B smallresponse demand signal (FIG. 13), the B code is no more received but theA code is continuously received on the vehicle. Step S171 only of thewelcome process repeats judging “YES”. Accordingly, the variable I isupdated to 2 at Step S173 and it is judged “YES” at Step S174. Theprocedure hence goes to Step S176 for locking the door.

When the A code is next received from the entry key, the procedure jumpsfrom S174 to S180 and then from S181 to S185. As it is judged “NO” atStep S185 before the setting time (for example, 30 seconds) of the BCHGtimer elapses, the procedure returns back to Step S2. When the settingtime has elapsed, however, it is judged “YES” at Step S185.

As a result, the procedure advances to Step S186 where the BSTM flag forselecting the B small response demand signal is turned to 0. At StepS187, the BLTM flag for selecting the B large response demand signal isturned to 1. Accordingly, the transmission of the B large responsedemand signal is initiated by timer interruption. As the entry key isfar enough away the vehicle and out of the communication area of the Blarge demand signal at the time, it is disabled to receive the B largeresponse demand signal and sends back non of the B code.

As the entry key departs further from the vehicle, it is disabled toreceive finally the A response demand signal and thus to release the Acode. This causes Step S14 of the procedure to judge “NO” and theprocedure moves via Step S15A shown in FIG. 4 to Step S30 shown in FIG.5. Then, Block S41 follows in which the flags are examined at Steps S31and S32 before the T-OUT timer is set to m seconds at Step S33, asdescribed previously. As long as it is judged “NO” at Step S35, theprocedure always restarts from Step S2.

When the A code is no more sent back and it is thus judged “YES” at StepS35 after m seconds of the setting time on the T-OUT timer, i.e. anysent-back code from the entry key 50 is not received in a duration of mseconds, as illustrated in the flowchart of FIG. 5, the procedure movesto Steps S36 to S39 for initializing the AREC, BREC, BLTM, and BSTMflags to 0 which flags relate to the welcome process. The procedure thengoes to Step S40 where the OUT flag is turned to 1 to register that theentry key 50 is out of the communication area for the A response demandsignal. This is followed by the procedure returning back to Step S2 forrepeating the steps.

As the BLTM and BSTM flags are set to 0 at the time, the procedure isafter t8 in FIG. 3 and before t1 in FIG. 2 where the intermittenttransmission of only the A response demand signal is executed. Asapparent, the A response demand signal is not received by the entry keyand its response signal carrying the A code is not sent back.

Welcome Function Process at Embarkation

A case of the driver with the entry key 50 approaching and embarking thevehicle will now be explained. As the entry key moves from a far enoughpoint where the A response demand signal cannot be received to a nearpoint within the communication area for the A response demand signal, itreceives the A response demand signal and sends back the A code inresponse. When the A code is received by the vehicle, it is judged “YES”at Step S14 and the procedure goes to Step S15 for judgment whether thereceived code is the manual code or not.

When the judgment is affirmative, the procedure advances to Step S16 forexecuting the manual operation process. The received code is not assumednow to be the manual code and it is thus judged “NO” at Step S15. Theprocedure then moves to Step S17 where it is examined whether the manualSW is turned on or not. When so, the procedure returns back to Step S2.But it is now judged “NO” and the procedure goes to Step S18 forinitiating the welcome process shown in FIG. 9.

In the welcome process, “YES” at Step S171 and “NO” at Step S174 areprovided and the procedure jumps to Step S180. As “NO” is also given atStep S180, it is examined at Step S188 whether the BLTM flag is 1 ornot. At the time, the BLTM flag is not 1 and procedure moves to StepS189 where the BLTM flag is shifted to 1 to select the transmission ofthe B large response demand signal. Then at Step S190, the variable n isset to 1. While only the A code is received from the entry key, theabove steps are repeated (excepting that because “YES” is given at StepS188, Steps S189 and S190 are skipped). The A response demand signal andthe B large response demand signal are thus transmitted at theirrespective intervals of time.

As the driver steps closer to the vehicle, the entry key is enabled toreceive the B large response demand signal from the vehicle and sendback the B code. When the B code is received by the vehicle, it isjudged “NO” at Step S171 but “YES” at Step S201. Accordingly, the dooris unlocked at Step S204. As the A code has been received at that time,“YES” is given at Step S209 and the transmission of the I responsedemand signal is inhibited at Step S212. At next Step S214, the BCHGflag is shifted to 0 to inhibit the switching of the response demandsignal from the B large to the B small.

As the driver opens the door, steps in the vehicle, and closes the door,it is judged “YES” at Step S6 (FIG. 4). Then, the timer interruptionpermitting bit for permitting the transmission of the I response demandsignal is enabled at Step S8 to permit the timer interruptedintermittent transmission of the I response demand signal. At the time,the entry key is disabled to receive the A and B response demand signals(which are transmitted to only the outside of the vehicle) and hence,none of the A code and the B code are received by the vehicle.

The entry key 50 receives the I response demand signal and responds tosend back the I code. When the I code is received by the vehicle, theprocedure runs through Steps S14, S15, and S17 and enters at Step S18the welcome process shown in FIG. 9. As it is judged “NO” at both StepsS171 and 201, the procedure advances to Step S221 shown in FIG. 10. Ablock denoted by the chained line SC in FIG. 10 is a known immobilizingprocess.

It is examined at Step S221 whether the IMDONE flag indicating thecompletion of the immobilizing checkup is 1 or not. At the time, theimmobilizing checkup is not executed and the procedure goes to Step S222for executing the immobilizing checkup. In the immobilizing checkup, theI code received is examined whether it is valid or not as will beexplained later referring to FIG. 11. When so, the IMOK flag is turnedto 1. Step S223 follows where the immobilizing checkup result isexamined based on the IMOK flag whether or not it is all right.

When it is judged “NO” at Step S223, the operation of the engine isdisabled at Step S227. When it is “YES”, the procedure goes to Step S224for permitting the start of the engine. At Step S225, the ATM flag isshifted to 0 and at Step S226, the AREC flag is shifted to 0. In thenext cycle of receiving the I code, it is judged “YES” at Step S221. Theprocedure then moves to Step S228 where the timer interruptionpermitting bit for the I response demand signal is cleared off toprohibit the intermittent transmission of the I response demand signal.

The bit information of the IMOK flag is transferred via thecommunication line (bus) 32 to the FI-ECU 33 (See FIG. 1). In responseto the bit of the IMOK flag, the FI-ECU 33 controls the action of a fuelpump, a fuel injector, a fuel feeder, and an ignition device (each notshown) in any known manner so that when the bit is 1, the engine isenabled and while when 0, the engine is disabled.

The blocks enclosed with the chain line SB in FIG. 9 are provided forassigning different levels of hysteresis to the communication area forthe B response demand signals at the embarkation and the disembarkation,and selecting the B small response demand signal when the driver getsaway from the vehicle for permitting the door locking at earlier timingand while the B large response demand signal when the driver approachestowards the vehicle for permitting the door unlocking at possiblyearlier timing. It would hence be appreciated that when the hysteresisis not applied, the blocks for switching between the B small signal andthe B large signal is unnecessary.

When the driver embarks and the IGN SW is turned on, it is judged “YES”at Step S2 in FIG. 4 and the procedure moves to Step S21 where are fresh2 process for initializing the welcome function flags is executed aswill be explained lately in more detail referring to FIG. 8. It is thenexamined at Step S22 whether the IMOK flag is 1 or not (i.e. the resultof the immobilizing checkup is all right or not).

If it is judged “NO” at Step S22, the procedure goes to Step S24 fordisabling the operation of the engine.

It is then examined at Step S25 whether the IMDONE flag is 1 or not(i.e. the immobilizing checkup is finished or not). When judged “NO”,the procedure moves to Step S26 where the timer interruption permittingbit for permitting the transmission of the I response demand signal isenabled similar to Step S8. Then, the immobilizing checkup processexplained later in conjunction with FIG. 11 is executed at Step S27. Theprocedure goes from Step S2 to Step S22 thereafter. In the immobilizingcheckup process, when the immobilizing code received by the vehicle isqualified to be judged that its key operation is correct, the IMOK flagis shifted to 1. It is hence judged “YES” at Step S22.

By now, the checkup is right and the procedure advances to Step S23 forenabling the start of the engine. As the IMDONE flag is set to 1 in theimmoblizing checkup process mentioned above, “YES” is given at Step S25.The procedure then goes to Step S28 where the timer interruptionpermitting bit for the I response demand signal is cleared off toprohibit the transmission of the I response demand signal. During therunning of the vehicle, the IGN SW remains turned on, the above stepsare repeated.

When the IGN SW is turned to the ACC or OFF position to stop the engine,it is judged “NO” at Step S2. The procedure then moves to Step S3 forexecuting the above described process at the disembarkation.

The transmission of the response demand signals in the welcome processwill be explained referring to FIG. 6. This process is executed in everyx seconds by the timer interruption to intermittently transmit the A orB (B large or B small) response demand signal, provided that theresponse demand signal transmission selecting flag is 1. The A, B large,and B small response demand signals may be selected as previouslydescribed referring to FIGS. 2, 3, and 13.

The procedure starts with Step S91 for examining whether MOD(n,3) iszero or not. MOD(n,3) is the remainder of the variable n divided by 3,which n is described previously concerning with Steps S190 and S211.When MOD(n,3) is zero, the procedure goes to Step S92 where it isexamined whether the ATM flag is 1 or not. When so, the procedure goesto Step S93 for permitting the transmission of the A response demandsignal.

When the remainder of n/3 is 1 or 2, it is judged “NO” at Steps S91 orS92 and the procedure moves to Step S94 where the BTSM flag is examinedwhether it is 1 or not. When so, the procedure goes to Step S95 forpermitting the transmission of the B small response demand signal. Whenjudged “NO” at Step S94, the procedure moves to Steps S96 for examiningwhether the BLTM flag is 1 or not. When so, the procedure advances toStep S97 for permitting the transmission of the B large response demandsignal.

The refresh 1 process at Step S3 (FIG. 4) will now be explainedreferring to FIG. 7. At Step S101, the RF1 (refresh 1) flag is examinedwhether or not it is 1 as indicating that the refresh 1 process iscompleted. When judges “YES”, i.e. the refresh 1 process is completed,the procedure jumps to EXIT. In the beginning, it is judged “NO”. Atnext Step S103, the IMOK flag is shifted to 0 and at Step S104, theIMDONE flag (immobilizing checkup is done) is shifted to 0. At StepS105, the IMCHK flag (immobilizing checkup is started) is reset to 0.

As the result, the initialization of the immobilizing checkup flags iscompleted. At Step S109, the RF1 flag is turned to 1 to register thatthe refresh 1 process has been done. At Step S110, the RF2 flag isturned to 0 to register that the refresh 2 process is not yet done.

The refresh 2 process at Step S21 (FIG. 4) will be explained in moredetail referring to FIG. 8. At Step S121, the RF2 flag is examinedwhether it is 1 or not, i.e. the refresh 2 process has been done or not.When “YES”, the procedure jumps to EXIT. When judged “NO”, the procedureruns through Steps S122, S123, and S124 for resetting the ATM, BLTM, andBSTM flags to 0, respectively. Those steps are to inhibit thetransmission of the A, B large, and B small response demand signals,respectively.

This is followed by Steps S125 and S126 for resetting the AREC and BRECflags to 0, respectively. These two steps are provided for registeringthat the code, which is included in a response signal send back from theentry key 50 in response to the reception of the demand signaltransmitted from the vehicle, is not yet received by the receiver on thevehicle. At Step S128, the variable n for determining the responsedemand signal to be transmitted is turned to zero.

At Step S129, the OUT flag is shifted to 0 (denied) for indicating thatthe entry key 50 is out of the communication area of the A responsedemand signal. At Step S130, the RCHK flag is set to 0 to indicate thatthe T-OUT timer is not started which sets the limited time for detectingwhether or not the entry key 50 is out of the communication area for theA response demand signal. At Step S131, the timer interruptionpermitting bit for the response demand signal is cleared off to inhibitthe timer interrupted transmission.

After the above steps, the initialization of the welcome function flagsare completed. Then, Step S135 follows where the RF2 flag is turned to 1to register the completion of the refresh 2 process. At Step S136, theRF1 flag is reset to 0 for registering the non-completion of the refresh1 process.

The immobilizing checkup process at Step S222 (FIG. 10) will beexplained in more detail referring to FIG. 11. The immobilizing checkupprocess starts with Step S230 for examining whether the IMCHK flag forindicating the starting of the immobilizing checkup process is 1 or not.When the immobilizing checkup process is not started and “NO” is given,the procedure moves to Step S235 for setting the immobilizing checkuptimer T-IMCHK to a desired immobilizing checkup period (for example, 30seconds). At Step S236, the IMCHK flag is shifted to 1.

When the immobilizing checkup process has been started and it is judged“YES” at Step S230, the procedure advances to Step S231 for examiningwhether or not the immobilizing code I sent back from the entry key isidentical to the code previously saved in a memory on the vehicle. Whenso, the procedure goes to Step S232 where the IMOK flag is turned to 1to indicate the confirmation of the immobilizing code comparison andStep S233 follows. Those steps allow the FI-ECU 33 to positively controlthe operation of the engine as described previously.

When judged “NO” at Step S231, the procedure goes to Step S246 forexamining whether the IMCHK timer is timed up or not. When not, theimmobilizing checkup process is terminated. When judged “YES” at StepS246, the procedure goes to Step S233. At Step S233, the IMDONE flagindicating that the immobilizing checkup process has been done is turnedto 1.

FIG. 12 illustrates the intermittent transmission of the I responsedemand signal with the timer interruption permitting bit for the Iresponse demand signal being enabled, where the timer interruption maybe carried out in every z seconds. The procedure starts with Step S271for examining based on the IMDONE flag whether the immobilizing checkupprocess is done or not. If not, the procedure goes to Step S272 forpermitting the transmission of the I response demand signal. When theimmobilizing checkup process has been done and it is judged “YES” atStep S271, the procedure is terminated.

According to the embodiment mentioned above, only when the entry keysends back a signal in response to reception of the A response demandsignal transmitted from the vehicle at longer intervals in the widercommunication area, and the signal thus sent back is received by thereceiver on the vehicle and confirmed to be correct response signalthrough the welcome code examination, the B response demand signal forthe smaller communication area is transmitted at least once in theperiod of transmitting two of the A response demand signals. In otherwords, even if any other person or object not carrying the entry key andunrelated to the vehicle moves into the A (response demand signalcommunication) area shown in FIG. 13, the transmission of the B responsedemand signal is not executed.

Accordingly, the occasion of transmitting the B response demand signalfor actually controlling the unlocking and locking action of the door isminimized, hence decreasing the power consumption of the vehiclebattery. Also, the interval between transmitting timings of two responsedemand signals is significantly minimized, thus allowing the position ofthe entry key relative to the vehicle to be more accurately identified.As a result, the transmission of the B response demand signal atintervals of an optimum period and in an optimum or relatively smallersize of the communication area can be executed without largelyincreasing the power consumption thus to precisely control the vehiclemounted components, for example, the automatic unlocking and lockingaction of the door of the vehicle, corresponding to the distance betweenthe entry key and the vehicle. More particularly, the precise controlover the vehicle mounted components with the entry key can successfullybe conducted in compatibility with the favorable energy saving.

The foregoing embodiment is based on the use of the B response demandsignals common to all the doors of a vehicle in conjunction with theirresponse signals. In that case, it may happen that when the entry keysteps in such a predetermined communication area as denoted by the B(large) in FIG. 13, all the doors are unlocked at same time.

For avoiding such an event, an alternative embodiment is provided asshown in the schematic view of FIG. 14 where three different B responsedemand signals B1, B2, and B3 respectively assigned to two of left andright doors 2 a, 2 b and a rear trunk door 2 c are provided. Forexample, when any one of the three B response demand signals is notreceived, all the doors are locked simultaneously. On the other hand,desired one of the doors can be unlocked by the controlling action of avehicle mounted receiver which receives a B code for the desired doorincluded in a response signal to the B response demand signal assignedto the desired door.

It should be understood by those skilled in the art that for applyingthe B response demand signals assigned to their respective doors, StepS201 in the flowchart of the welcome process shown in FIG. 9 may bemodified to examine the received code for its matching with an uniquecode assigned to the desired door. Hence, the modification of theflowchart will be explained in no more detail. It is also appreciatedthat different levels of the hysteresis may be allocated to the sizes ofthe communication areas between the unlock and lock operation.

FIG. 15 illustrates an exemplary format of the response signalapplicable to the above- and under-mentioned embodiments of the presentinvention. As shown, CDA is a start bit, CDB is an identification code,CDID is an ID code uniquely assigned to each vehicle, and CDF is afunction code. The figures in the parenthesis represent the numbers ofbits of the codes. In general, the ID code is used for examining if anentry key is authentic, while the function code is for discriminatingthe A and B codes from each other. The function code may be comprised offour bits, respectively; for example, the A code is [1000], the B code[1001], the manual lock code [1100], and the manual unlock code [1101],respectively in the case of FIG. 13, while the A code is [1000], the Bcode for the driver's door [1001],the B code for the passenger's door[1010], and the B code for the trunk door [1011] in the case of FIG. 14.

FIG. 16 illustrates an exemplary format of the response signal for the(anti-thief) immobilizing function applicable to the embodiments of thepresent invention. As the code comparison for the immobilizing functionis extremely important for ensuring the anti-thief action as well known,it may preferably be differentiated in the structure from the othercodes. As shown, CDA is a start bit, CDB is an identification code, andCDIM is an immobilizing function ID code. It is also possible to haveall types of the response signals designed to a single particularlystructured format.

Although the hysteresis characteristic is assigned to the communicationareas for the B response demand signal between the unlock mode and thelock mode, the present invention is not limited to always have thehysteresis characteristics. The B large response demand signal and the Bsmall response demand signal shown in the schematic view of FIG. 13 andthe timing charts of FIGS. 2 and 3 may be a single and common B responsedemand signal.

As for a further embodiment of the present invention using the singleand common B response demand signal, a flowchart of its main procedure(corresponding to FIGS. 4 and 5) is shown in FIGS. 17 and 18 while aflowchart of its welcome function process (corresponding to FIG. 9) isshown in FIG. 19. Throughout the figures, like components are denoted bylike numerals as those shown in FIGS. 4, 5, and 9 and will be explainedin no more detail but only different steps or blocks will be explainedbelow.

At Step S12B in FIG. 17, the B response demand signal selecting flag BTMis shifted to 1 for enabling the timer interrupted transmission of the Bresponse demand signal. At Step S38B in FIG. 18, the flag BTM is resetto 0 to inhibit the transmission of the B response demand signal. StepS186B in FIG. 19 is provided for examining whether the flag BTM is 0 ornot. The flag BTM is turned to 1 at Step S188B to permit thetransmission of the B response demand signal, preparing for unlocking ofthe door as the driver comes towards the vehicle. When the entry keydeparts further from the vehicle and it is disabled to receive even theA response demand signal, the intermittent transmission of the Aresponse demand signal only is maintained as described with the previousembodiment.

As the entry key 50 comes close to the vehicle, it receives the Aresponse demand signal and sends back the A code. When the A code isreceived by the vehicle mounted receiver, it is judged “YES” at StepS171, “NO” at Step S174, and “YES” at Step S186B similar to those of theprevious embodiment. Accordingly, Step S188B permits the transmission ofthe B response demand signal. The succeeding procedure may clearly beunderstood from the forgoing descriptions.

FIG. 20 is a flowchart showing the timer interrupted transmission of theA and B response demand signals executed in the welcome process of thisembodiment. This drawing is similar to FIG. 6 in which like blocks aredenoted by like numerals as those shown in FIG. 6 and they will beexplained in no more detail. It is examined at Step S91B whether MOD(n,2) which is the remainder of n/2 is zero or not (i.e. n is an odd numberor an even number). When judged “NO” or n is an odd number, theprocedure goes to Step S94B for examining whether the flag BTM forpermitting the timer interrupted transmission of the B response demandsignal is shifted to 1 or not.

When so, the transmission of the B response demand signal is permittedat Step S95B and procedure moves to Step S98. When it is judged“NO” atStep S94B, n is updated at Step S98 before the procedure of this processis terminated. The divisor such as 2 or 3 used at Steps S91B and S91 maypreferably be determined so that the transmission of the response demandsignals is timed favorably with the interval of the timer interruptionsettings (x or x′ seconds).

Although the response demand signal transmitted from the vehicle mountedreceiver is classified into two different types, A and B, for the widerand the narrower communication areas respectively in the previousembodiments, the prevent invention may employ three or more types of theresponse demand signals for different sized communication areas. FIGS.21A and 21B are timing charts illustrating the transmission of threedifferent types of the response demand signal.

As shown, while the A response demand signal for the widestcommunication area is transmitted at intervals of the longest period y,the B response demand signal for the second widest communication area istransmitted, for example, at every intermediate moment between twoadjacent transmitting timings of the A response demand signal, providedthat the A code is received by the vehicle, indicating that the Aresponse demand signal is successfully received by the entry key whichis moving towards the vehicle.

The C response demand signal for the smallest communication area is alsotransmitted at every intermediate moment between the A response demandsignal and the B response demand signal, provided that the B code isreceived indicating that the B response demand signal is successfullyreceived by the entry key which is moving towards the vehicle. Thosecodes in the response signals may be expressed as, for example, the Acode [1000], the B code [1001], the C code [1011] and the I code [0101].

On the other hand, when the driver disembarks and the entry key departsfrom the vehicle, the response signal responding to the C responsedemand signal for the smallest communication area will first becomeimpossible of being received, then the response signal to the B responsedemand signal for the medium sized communication area, and finally theresponse signal to the A response demand signal for the widestcommunication area. The interval between two adjacent receptions of theresponse signals will thus be increased step by step.

In this embodiment, the response signal carrying the response code (oneof the A, B, and C codes) is send back from the portabletransmitter/receiver of the entry key corresponding to which one of theresponse demand signals for the communication areas of different sizesis received by it, hence allowing the control unit on the vehicle tointimately identify the location of the entry key relative to thevehicle. Accordingly, the vehicle mounted components can favorably becontrolled depending on the distance from the vehicle to the entry keydetermined on the basis of the code in the response signal sent back.

As will be understood from the timing chart of FIGS. 21A and 21B, theresponse codes are received at intervals of a shorter period or at ahigher rate of frequency from the entry key which is in a positioncloser to the vehicle. The location of the entry key relative to thevehicle can thus be identified by measuring the receiving cycle orfrequency of the response codes on the vehicle. Also, as the entry keyis in the position closer to the vehicle, the receiving cycle will beexpected to be shorter thus possibly making the response action of thevehicle mounted components quicker.

Although the above-mentioned embodiments include transmitting from thevehicle mounted transmitter different types of the response demandsignals which are different in the size of the communication area andthe characteristics, sending back from the entry key the response codescorresponding to the type or the communication area of the responsedemand signal received, and identifying on the basis of the receivedresponse code the location of the entry key relative to the vehicle, thedifferent types of the response demand signals may be designed uniformlyin the characteristics and their response codes for simplification ofthe signal structure, when they are transmitted from the vehicle mountedtransmitter at their respective frequencies or repetitive cyclesdifferent each other in their corresponding sizes of the communicationareas as shown in FIGS. 21A and 21B.

Subsequently, the distance of the entry key from the vehicle cansuccessfully be identified from the receiving intervals, thefrequencies, or repetitive cycles of the response signal (response code)received by the vehicle mounted receiver and used for favorablycontrolling the operation of the vehicle mounted components according tothe distance identified. An embodiment of the above modification willnow be described referring to FIGS. 22 and 23. In these two graphs, theheight of the different types of the response demand signals WS and WLrepresents only the intensity of the signal which is the size of thecorresponding communication area.

FIG. 22 is a time chart showing schematically the actions when thedriver carrying the entry key disembarks and walks away from thevehicle. As the vehicle 1 stops, the IGN SW is turned at t1 from the ONposition to the ACC position and the door is opened at t2 by the driverfor disembarkation. Then, the door SW is shifted from the OFF (open)position to the ON (close) position. This triggers the transmission ofthe W small response demand signal WS for a narrow communication area.The W small response demand signal WS is transmitted from the vehiclemounted transmitter at the predetermined intervals of 2 u.

When the entry key 50 steps out from the vehicle and is enabled toreceive the W small response demand signal WS, it releases a responsesignal carrying the W code (referred to as W code hereinafter) As the Wcode is received and the welcome code comparison is confirmed at t3, afirst timer TWR1 for the receiving interval is set to a period v andthen initiated. Simultaneously, the intermittent transmission of the Wlarge response demand signal WL is initiated, of which the communicationarea is greater than that of the W small response demand signal (i.e.the transmitting output is higher while the other characteristics areidentical to WL).

In this embodiment, the W large response demand signal WL is transmittedat every intermediate moment between two transmitting timings of the Wsmall response demand signal WL and hence at the intervals equal to 2 useconds as illustrated. The setting time v of the timer may preferablybe equal to the minimum transmitting interval (u) between the adjacenttwo response demand signals WS and WL.

This setting is preferable but not necessary. It is simply required totransmit the two response demand signals WS and WL alternately and moregenerally, to clearly discriminate the difference between an interval oftransmitting timings when only the W large response demand signal WL istransmitted and the other interval when both of the W large and smallresponse demand signal WL and WS are transmitted (preferably, the latteris shorter). In practice, the setting time v may preferably be set to(u+Δu) seconds considering various unevenness in the system.

As the welcome code comparison is confirmed at t4 with the W codereceived, a second timer TWR2 for the receiving interval is set to v andinitiated. Simultaneously, it is examined whether the first timer TWR1is timed up or not. As apparent from the criteria for setting the twotimers, the two timers are not timed up while the W large and smallresponse demand signal WL and WS are successfully received by the entrykey which in turn releases their corresponding response signals W.

As the entry key 50 departs further from the vehicle and receives nomore the W small signal WS, the vehicle mounted receiver is disabled toreceive its response signal. One of the timers TWR (namely, the secondtimer TWR2 in this case) is then timed up to be turned to zero at t5. Asthe W code responding to the W large response demand signal is receivedand the welcome code comparison is confirmed at t6, the first timer TWR1is restarted and the time up of the second timer TWR2 is acknowledged.

It is hence determined that the receiving interval of the W code islonger than v, i.e. the entry key is out of the communication area ofthe W small response demand signal WS, allowing the door of the vehicleto be locked. When the W code is not received within m seconds of thepreset time after the locking action, the transmission of the W smallresponse demand signal WS is stopped and the intermittent transmissionof only the W large response demand signal WL is continued.

Referring to FIG. 23, the actions when the driver comes towards thevehicle 1 and its location is detected will be explained. When the entrykey is out of and significantly distanced from the vehicle with the doorlocked in its disembarkation or parking mode, the W large responsedemand signal WL for the wider communication area is being transmittedat the predetermined intervals (of 2 u seconds) from the vehicle asdescribed previously and shown at the left most portion in FIG. 23. Asthe driver carrying the entry key steps into the communication area ofthe W large response demand signal WL about the vehicle, the entry keyreceives the W large response demand signal WL at t1.

Then, the entry key send back the W code responding to the reception ofthe W large response demand signal WL. As the W code is received by thevehicle and determined at t2 by the welcome code comparison that it isvalid, the vehicle mounted control unit starts the first timer TWR1 forthe receiving interval and simultaneously transmits the W small responsedemand signal WS at the equal interval (of 2 u) and at everyintermediate moment between two adjacent transmitting timings of the Wlarge response demand signal WL.

When the W code which is released from the entry key responding toreception of the W large response demand signal at t3 prior to thereception of the W small response demand signal WS is received andjudged by the welcome code comparison that it is valid, the second timerTWR 2 for the receiving interval is started. At the time, the firsttimer TWR1 is timed up and the door is not unlocked.

As the entry key 50 comes close enough to receive the W small responsedemand signal WS, it releases the corresponding W code. Upon the W codereceived and judged that it is valid, the second timer TWR2 is startedat t4 and it is determined that the first timer TWRL is not timed up.Then, the door of the vehicle is unlocked. When the door is opened (thedoor SW turned on) and then closed at t5, it is determined that thedriver is in the vehicle. Then, the transmission of the I (immobilizing)response demand signal is initiated for its communication area limitedwithin the vehicle (not shown in FIG. 23).

As the entry key releases the immobilizing code (I code) in response tothe I response demand signal, the immobilizing code is received andexamined by the vehicle. When it is judged that the I code is valid, thetransmission of the I response demand signal is stopped thus enablingthe start of the engine. As the ignition SW is turned to the ON positionat t6, the transmission of both the response demand signals WL and WS isstopped and simultaneously the refresh 2 process is initiated as will beexplained later.

The transmission of the response demand signals WL and WS may be stoppedwhen it is judged that the I code is valid. The response demand signalis not limited to the two types, WL and WS, and may be classified intothree or more types which are different from each other in the size ofthe communication area and the transmitting interval.

A detailed procedure of this embodiment will now be described referringto its main flowcharts of FIGS. 24 and 25 and its welcome processflowchart of FIG. 26. In these drawings, the contents of process inblocks denoted by same numerals are identical to those in FIGS. 4, 5,and 9 and will be explained in no more detail but their differentaspects.

Referring to FIG. 24, when the driver opens the door for disembarkation,the procedure goes from Step S10 to Step S11W for examining whether theWREC flag is 1 or not, i.e. the W code is received or not from the entrykey 50. At the disembarkation, this step judges “NO” and the WSTM flagis turned to 1 at Step S12W to select the transmission of the W smallresponse demand signal WS. Step S13 follows for enabling theintermittent transmission of the W small response demand signal WS withtimer interruption.

The timer interruption for the intermittent transmission is carried outat the interval of u seconds as clearly illustrated in FIGS. 22 and 23.More specifically, the A and B response demand signals in the flowchartof FIG. 20 are replaced with the W large and W small response demandsignals WL, WS, respectively. As the driver or the entry key steps outfrom the vehicle and receives the W small response demand signal, itsends back the W code in response. The W code is then received by thevehicle mounted receiver allowing Step S14 to judge “YES” and thewelcome process at Step S18 follows.

FIG. 26 illustrates the flowchart of the welcome process which is to becombined with FIG. 10. The operation is first explained when the driverdisembarks and its entry key departs from the vehicle. As the W codetransmitted from the entry key responding to the reception of the Wsmall response demand signal WS from the vehicle is received by thevehicle, it is judged “YES” at Step S301 and the procedure goes to StepS302. If it is judged “NO”, the procedure jumps to Step S221 in FIG. 10.At Step S302, the WREC flag indicating the reception of the W code isshifted to 1.

This is followed by a sequence of Steps S303 to S306 for updating by onethe count of the W counter which represents the number of receptions ofthe W code (the count incremented to 1 by the first reception), shiftingthe WLTM flag to 1 for selecting the transmission of the W largeresponse demand signal, turning the OUT flag to 0 for registering thatthe entry key is within the communication area of the W large responsedemand signal WL, and resetting the timer TOUT setting time fordetecting that the entry key is no more close to the vehicle,respectively.

Then, it is examined at Step S307 whether the count of the W counter is1 or not. As the count is 1 and judged “YES” by now, the procedureadvances to Step S308 for setting and initiating the first timer for thereceiving interval with the time v and then returns back to Step S2 inFIG. 24. At the next cycle of receiving the W code, Steps S307 judges“NO” and the procedure goes to Step S309 where it is examined whetherthe remainder of the count of the W counter divided by 2 is 0 or not,i.e. whether the count of the W counter is an odd number or an evennumber.

As the count is 2 and it is judged “YES”, the second timer TWR2 isequally set to v and initiated at Step S310. Then, Step S311 follows forexamining whether the first timer TWR1 is counted up or not. Asdescribed previously referring with FIG. 22, the W codes arecontinuously released in response to the W large and small responsedemand signals WL and WS for a while after the disembarkation and canthus be received before the timers are timed up. Accordingly, Step S311judge “NO”.

Therefore, the procedure advances to Step S312 for maintaining theunlocked state of the door. When the reception of the next W codeincreases the count of the W counter to 3, the procedure goes from StepS309 to Step S314 for setting and initiating the first timer TWR1 withthe time v. It is then examined at Step S315 whether the second timerTWR2 is counted up or not.

While the entry key departs not far enough from the vehicle, Step S315judges “NO” as described above and the unlocked state of the door ismaintained at Step S312. When the entry key departs far enough from thevehicle and is disabled to receive the W small response demand signalWS, it is then judged “YES” at Step S315 and the procedure goes to StepS316 where the door of the vehicle is locked. Also, when Step S311judges “YES” upon an even number of receiving times of the W code, thedoor is locked at Step S318.

As the entry key 50 departs further from the vehicle, it is disabled toreceive the W large response demand signal WL and fails to deliver thecorresponding W code to the vehicle. It is then judged “NO” at Step S14in FIG. 24 and the procedure goes from Steps S15A and S30 to Step S35.At the time, Step S35 judges “YES” and the initialization is executed atSteps S36W to S39W and S40. More particularly, the W counter is reset tozero, the first timer TWR1 and the second timer TWR2 are reset, the WSTMflag is turned to 0, and the OUT flag is shifted to 1.

The action of automatically unlocking the door will now be explainedwhen the driver carrying the entry key 50 moves towards the vehicle forembarkation. As the entry key 50 steps into the communication area ofthe W large response demand signal WL and receives the signal WL, itreleases the corresponding W code. When the W code is received for thefirst time and judged at Step S301 in FIG. 26 that it is valid, the sameprocess at Steps S302 to S307 are repeated.

More specifically, the W counter is reset to 1, the WLTM flag is shiftto 1, the OUT flag is shifted to 0 for registering that the entry key iswithin the communication area, and the timer T-OUT is reset. At thetime, Step S307 judges “YES” and the first timer TWR1 is set to v atStep S308 before the welcome process is terminated.

As the reception of the next W code causes Step S307 to judge “NO” andStep S309 to judge “YES”, the second timer for the receiving intervalTWR2 is set with v at Step S310. Step S311 follows where it is judged“YES” because the entry key 50 receives only the W large response demandsignal WL and the interval of the W code is long enough, hencemaintaining the locked state of the door.

Also, when the procedure goes from Step S309 to Steps S314 and 315, thelocked state of the door is maintained at Step S316. As the entry keycomes closer to the vehicle and receives too the W small response demandsignal WS, Step S311 or S315 judges “NO” permitting the door to beunlocked.

When the driver opens the door, steps into the vehicle, and shuts up thedoor, it is then judged “YES” at Step S6 (FIG. 24) and the timerinterrupted transmission of the I response demand signal is enabled atStep S8. As described with the first embodiment, when the I codecomparison is confirmed, the action of the engine is enabled. As theignition switch IGN SW is turned by the driver to the ON position, theengine starts running and simultaneously, the transmission of the Wresponse demand signals and the I response demand signal is stopped.Then, the flags are initialized at the steps in Block S41 (FIG. 25).

According to this embodiment, while the two types, WL and WS, of theresponse demand signal can successfully be switched from one to anotherby changing only the output level of the response demand signal from thevehicle mounted transmitter, the response code released from the entrykey is used only of one type, W code. Therefore, the transmitter andreceiver arrangements as well as the code identification function willsignificantly be simplified, thus contributing to the lower cost and theease of maintenance.

Although both the unlocking and locking actions of the door areautomatically controlled according to the reception of response signalto the response demand signals on the vehicle mounted receiver in theembodiments mentioned above, it will clearly be understood by thoseskilled in the art to automate only one of the two actions for moresimplicity.

According to the present invention recited in claims 1 and 2, thedistance from the vehicle to the user carrying the portabletransmitter/receiver (entry key) can precisely be identified thus tocontrol the vehicle mounted device such as the door(s) at an optimumlength of the distance, hence improving the utility of controlling thevehicle mounted device such as unlocking and locking the door(s) iscompatible with improvement in the anti-thief function.

According to the present invention recited in claim 3, the distance fromthe vehicle to the user carrying the portable transmitter/receiver canbe identified on the basis of the interval between receiving timings ofthe sent-back response signal on the vehicle even if the characteristiccodes included in the response signals are not different each other,which response signals are sent back from the portabletransmitter/receiver in response to a plurality kinds of the responsedemand signal receivable within their respective sizes of thepredetermined ranges which are different each other. Hence, the vehiclemounted device can favorably be controlled depending on the distance aswell as the construction of the transmitter of the portabletransmitter/receiver and the code identifying action of the controllingmeans on the vehicle can significantly be simplified.

According to the present invention recited in claim 4, the responsesignal is also released at intervals of time from the portabletransmitter/receiver, thus providing the same effects and advantages asdescribed just above relating to the claim 3 invention.

According to the present invention recited in claim 5, as the responsesignals released from the portable transmitter/receiver in response toreception of the response demand signal are different each other basedon the different sizes of the receivable ranges of the demand signals,the distance from the vehicle to the portable transmitter/receiver canbe identified only from the response signal received and the optimumcontrol of the device mounted on the vehicle can be performed inaccordance with the distance.

According to the present invention recited in claims 6 and 7, at thedisembarkation of the user, as the portable transmitter/receiver carriedby the user departs far from the vehicle, the transmission of theresponse demand signal receivable in a predetermined wider size of therange is executed, while the transmission of the response demand signalreceivable in a predetermined smaller size of the range is canceled. Asthe potable transmitter/receiver comes from far towards the vehicle, onthe other hand, the transmission of the response demand signal with asmaller predetermined receivable range is not executed before theresponse signal responding to the response demand signal with thelargest predetermined receivable range is received by the vehicle.

More particularly, while the portable transmitter/receiver is out of thelargest predetermined receivable range, the response demand signalreceivable in the largest predetermined range only is transmitted. Onlywhen the response signal responding to the response demand signalreceivable in the largest predetermined range is received by thevehicle, the transmission of the response demand signal receivable in asmaller size of the predetermine range and used for actually controllingthe unlocking and locking of the door is executed. Therefore, thetransmission of the response demand signal is minimized hence reducingthe consumption of a power from a battery equipped on the vehicle.

According to the present invention recited in claim 8, the user carryingthe portable transmitter/receiver in the vehicle can precisely beacknowledged, and the vehicle mounted device in the vehicle iscontrolled on the basis of the response signal from the portabletransmitter/receiver responding to a particular type of the responsedemand signal receivable within the vehicle, hence improving theanti-thief function.

In brief, the present invention allows the entry key to receive theresponse demand signal for a wider communication area and send back aresponse signal to the vehicle, and the vehicle to transmit the responsedemand signal for a smaller communication area only when the responsesignal from the entry key is examined and qualified to be valid by itswelcome code comparison. In other words, even if any other person orobject not relating to the vehicle is within the communication area Ashown in FIG. 13, no transmission of the B response demand signal ispermitted.

Accordingly, the transmission of the B response demand signal foractually controlling the locking and unlocking action of the door isminimized hence favorably reducing the consumption of a power in thebattery. Also, while the power consumption is minimized, thetransmission of the response demand signals can be executed at optimumintervals of time for a relatively smaller size of the communicationarea corresponding to the distance from the entry key to the vehiclethus to precisely control the vehicle mounted components, for example,automatically unlocking and locking the door of the vehicle. Moreparticularly, the control over the vehicle mounted components with theentry key can be made in compatibility with the energy saving. Inpractice, while the power consumption is minimized, the anti-thieffunction can be realized at higher utility.

Moreover, as different types of the response demand signals aretransmitted from the vehicle at intervals of time, the transmission ofthe response demand signal for a wider communication area is executed atintervals of a longer duration. This permits the control system toreadily acquire the distance from the vehicle to the entry key on thebasis of the interval between receiving timings of the response signalfrom the entry key without discriminating the response demand signalsand the response signals received, respectively, from each other andthus to favorably control the vehicle mounted components such as doors.Accordingly, the overall system can further be simplified inconstruction and operation.

1. A remote control system for a vehicle comprising: a transmittermounted on the vehicle for transmitting a response demand signalreceivable within a predetermined range outside the vehicle; a portabletransmitter/receiver for sending back a response signal in response toreception of the response demand signal; a receiver mounted on thevehicle for receiving the response signal sent back from the portabletransmitter/receiver; and a controlling means for controllingvehicle-mounted components responding whether the receiver receives theresponse signal or not, said transmitter arranged to transmit aplurality of response demand signals receivable within differentcorresponding predetermined ranges, said controlling means arranged toidentify that the portable transmitter/receiver exists within thelargest predetermined receivable range and to make the transmittertransmit another response demand signal receivable within apredetermined range which is smaller than the largest size of thepredetermined range in addition to the response demand signal receivablein the largest size of the predetermined range when a response signal isreceived by the receiver, which response signal corresponds to receptionof particular response demand signal being receivable within the largestpredetermined receivable range and, to control at least either unlockingor locking of a door(s) of the vehicle depending on whether a responsesignal is received or not by the receiver, which response signalcorresponds to reception of the other response demand signal than aparticular one being receivable within the largest predeterminedreceivable range.
 2. A remote control system for a vehicle according toclaim 1, further comprising a disembarkation detecting means fordetecting the disembarkation of a user, wherein when the disembarkationof the user is detected, a response demand signal receivable within thesmallest size of the predetermined range is transmitted from thetransmitter, and when the response signal showing reception of theresponse demand signal receivable in the smallest size of thepredetermined range is no more received by the receiver mounted on thevehicle, a second response demand signal receivable within the secondsmallest size of the predetermined range is begun to be transmitted fromthe transmitter in addition to the response demand signal receivable inthe smallest size of the predetermined range and, in a similar manner, aresponse demand signal receivable within a relatively larger size of thepredetermined range is transmitted in sequence from the transmitter. 3.A remote control system for a vehicle according to claim 1 wherein whenthe response signal to the response demand signal receivable within thelargest size of the predetermined range is received after it is notreceived by the receiver mounted on the vehicle, the response demandsignal receivable within second largest size of the predetermined rangeis transmitted from the transmitter in addition to the response demandsignal receivable within the largest predetermined range and then aresponse demand signal receivable within a relatively smaller size ofthe predetermined range is transmitted in sequence from the transmitter.4. A remote control system for a vehicle according to claim 1 whereinfurther comprising an embarkation detecting means for detecting theembarkation of a user, wherein when the embarkation of the user isdetected by the embarkation detecting means, a response demand signalreceivable within the vehicle is transmitted from the transmitter, andwhen the response signal to the response demand signal receivable insidethe vehicle is received by the receiver, action of an engine is enabled.